1. Field of the Invention
The present invention relates generally to avionics systems and more particularly to improved switching systems for Avionics Full-Duplex Switched Ethernet (AFDX) systems.
2. Description of the Related Art
Modern onboard avionics networks serve to provide data transfer between various components of an aircraft. Avionics systems typically have a variety of systems that provide data to processing components of the aircraft or exchange data among one or more components of the aircraft. For example, a variety of avionics modules may gather avionics data (e.g., sensors detecting speed, direction, external temperature, control surface positions, and the like) that is routed by the avionics system via an avionics network to one or more aircraft components such as displays, monitoring circuits, processors, and the like. The speed of the physical media used to interconnect components is faster than the components' ability to receive the data. This serves as a barrier to entry of end systems.
In some aircraft systems, the avionics network may be constructed with an Aeronautical Radio Inc. (ARINC) 429 data bus capable of supporting communication between many components. More recently, Ethernet networks have been used in avionic network environments by leveraging Commercial Off-The-Shelf (COTS) technology to increase bandwidth and reduce cost.
Ethernet type networks have been used in communication networks for implementing communication among various network components. An Ethernet network may be used to send or route data in a digital form by packets or frames. Each packet contains a set of data, and the packet is generally not interpreted while sent through the Ethernet network. In an avionics network environment, the Ethernet network typically has different components that subscribe to the avionics network and connect to each other through switches. Each network subscriber can send packets in digital form, at controlled rates, to one or more other subscribers. When a switch receives the packets, the switch determines the destination equipment and directs or switches the packets to such equipment.
Such Ethernet networks may include ARINC-664 based networks. In a switched full-duplex Ethernet type network, the term “full-duplex” refers to sending and receiving packets at the same time on the same link, and the term “switched” refers to the packets being switched in switches on appropriate outputs. However, the ARINC-664 network uses multiple switches and redundant paths to route data, point-to-point or point-to-multipoint across the switches.
Avionics Full-Duplex Switched Ethernet (AFDX) is a data network for safety-critical applications that utilizes dedicated bandwidth while providing deterministic Quality of Service (QoS). AFDX is based on IEEE 802.3 Ethernet technology and utilizes Commercial Off-The-Shelf (COTS) components. AFDX is a specific implementation of ARINC Specification 664 Part 7, a profiled version of an IEEE 802.3 network per parts 1 & 2, which defines how Commercial Off-the-Shelf (COTS) networking components will be used for future generation Aircraft Data Networks (ADN). The six primary aspects of AFDX include full duplex, redundancy, deterministic, high speed performance, switched and profiled network.
Certain AFDX data networks require synchronous scheduling for proper operation. For example, U.S. Pat. No. 7,675,919, issued to S. C. Vestal, entitled, “End System Scheduling for Switched Networks,” discloses a method for scheduling one or more data packet transfers over a computer-based distributed network. The method involves constructing a cyclic schedule from a plurality of data packets, wherein the cyclic schedule is constructed to ensure that each data packet transfer is substantially free of jitter. The method further involves synchronizing the cyclic schedule with at least one periodic processing schedule and transmitting the synchronized data packets as arranged by the cyclic schedule.
U.S. Pat. No. 7,787,486, issued to S. C. Vestal, entitled, “Method and System for Achieving Low Jitter in Real-Time Switched Networks,” discloses a method and system for increasing the precision of time synchronization among a plurality of host nodes in a packet-switched network by reducing transmission delay variation in the network. Each host node is provided with a distinct set of transmission times selected from a global schedule in such a way as to avoid concurrent transmission of messages by the plurality of host nodes. The transmission times may be determined as offsets within a global hyperperiod, and each host node carries out transmissions according to predetermined offsets of the respective host node. Transmissions according to offsets may be applied to real-time messages, including time-synchronization messages, hence yielding increased precision of synchronization.
Some networks are designed for asynchronous operation between components. This provides cost savings. With such networks each end system is viewed as having a set of flows where each flow has an expected arrival envelope. It is desired that the number of virtual links (VLs) be maximized for a given level of performance.
Software based end systems may not support the line rate transmission rates from AFDX switches. This is true at 100 Mbps but will be more of a problem when 1 Gbps and 10 Gbps physical line rate capabilities are utilized. Even when software based end systems can support the line rate capability, this usually comes at a significant cost of reserved processor capacity needed to manage bursts of arriving data.
As will be disclosed below the present invention addresses issues faced when low capacity end systems are utilized in the network. As used herein the term “low capacity” end systems means systems that cannot process received frames as fast as they arrive.
U.S. Ser. No. 13/533,034, now issued as U.S. Pat. No. 8,817,622, entitled, “DATA NETWORK WITH AGGREGATE FLOW MONITORING,” filed concurrently herewith, by the applicants, D. A. Miller and D. E. Mazuk, and assigned to the present assignee, discusses the use of aggregate flow monitoring in a data network for monitoring the aggregate arrival data flow in defined traffic constraint envelopes containing frames. This co-filed patent application is incorporated by reference herein in its entirety.
U.S. Ser. No. 13/533,572, entitled, “DATA NETWORK WITH ‘PER FLOW’ FLOW MONITORING,” filed concurrently herewith, by the applicants, D. A. Miller and D. E. Mazuk, and assigned to the present assignee, discusses the use of “per flow” monitoring in a data network. This co-filed patent application is incorporated by reference herein in its entirety.